feat: add support for job, step shell override

WORKFLOW_SUPPORT.md

@@ -22,7 +22,7 @@ syntax](https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for
   - [ ] jobs.<job_id>.outputs
   - [x] jobs.<job_id>.env
   - [x] jobs.<job_id>.defaults
-    - [ ] jobs.<job_id>.run.shell
+    - [x] jobs.<job_id>.run.shell
     - [x] jobs.<job_id>.run.working-directory
   - [ ] jobs.<job_id>.timeout-minutes
   - [ ] jobs.<job_id>.strategy
@@ -40,7 +40,7 @@ syntax](https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for
     - [ ] jobs.<job_id>.steps[*].uses
     - [x] jobs.<job_id>.steps[*].run
     - [x] jobs.<job_id>.steps[*].working-directory
-    - [ ] jobs.<job_id>.steps[*].shell
+    - [x] jobs.<job_id>.steps[*].shell
     - [ ] jobs.<job_id>.steps[*].with
     - [x] jobs.<job_id>.steps[*].env
     - [X] jobs.<job_id>.steps[*].continue-on-error

internal/driver/driver.go

@@ -26,11 +26,14 @@ type CommandOptions struct {
 	// Note: In the case of container drivers, these mappings are applied within the
 	//  container.
 	Env map[string]string
+	// Shell to use when running the command.
+	Shell string
 }
 
 func NewCommandOptions() CommandOptions {
 	return CommandOptions{
 		Cwd:   ".",
+		Shell: "bash",
 		Env:   map[string]string{},
 	}
 }

internal/driver/podman_driver.go

@@ -95,7 +95,7 @@ func (d PodmanDriver) Exec(containerId string, command string, options CommandOp
 	commandArgs = append(commandArgs, envArgs...)
 
 	commandArgs = append(commandArgs, containerId,
-		"bash",
+		options.Shell,
 		"-c",
 		command,
 	)

internal/runner/runner.go

@@ -104,8 +104,8 @@ func (r Runner) runJob(jobContext context.Context, jobTracker *TaskTracker, jobW
 //
 // If the command raises an error while in the container or fails to run
 // the command at all, an error is returned, otherwise nil.
-func (r *Runner) RunCommandInContainer(containerId string, command string, stepCwd string, stepEnv map[string]string) error {
-	result := r.Driver.Exec(containerId, command, driver.CommandOptions{Cwd: stepCwd, Env: stepEnv})
+func (r *Runner) RunCommandInContainer(containerId string, command string, options driver.CommandOptions) error {
+	result := r.Driver.Exec(containerId, command, options)
 
 	if result.Error != nil {
 		return result.Error
@@ -133,15 +133,22 @@ func (r *Runner) RunJobInContainer(imageUri string, containerId string, jobConte
 
 	logger.Info("Started %s", containerId)
 	for stepIndex, step := range job.Steps {
-		stepCwd := jobContext.Value("workflow").(workflow.Workflow).GetWorkingDirectory(job.Name, stepIndex)
-		stepEnv := jobContext.Value("workflow").(workflow.Workflow).GetEnv(job.Name, stepIndex)
+		workflow := jobContext.Value("workflow").(workflow.Workflow)
+		stepCwd := workflow.GetWorkingDirectory(job.Name, stepIndex)
+		stepEnv := workflow.GetEnv(job.Name, stepIndex)
+		stepShell := workflow.GetShell(job.Name, stepIndex)
 
 		logger.Info("Run: %s", step.Run)
 		logger.Info("Using working directory %s", stepCwd)
 		var stepError error
 
 		if step.Run != "" {
-			stepError = r.RunCommandInContainer(containerId, step.Run, stepCwd, stepEnv)
+			commandOptions := driver.CommandOptions{
+				Cwd:   stepCwd,
+				Env:   stepEnv,
+				Shell: stepShell,
+			}
+			stepError = r.RunCommandInContainer(containerId, step.Run, commandOptions)
 		}
 
 		if stepError != nil && !step.ContinueOnError {

internal/runner/runner_flow_test.go

@@ -22,7 +22,7 @@ func TestRunnerRunCommandInContainerReturnsErrorFromDriver(t *testing.T) {
 		Driver: &mockDriver,
 	}
 
-	err := runner.RunCommandInContainer("test-container", "test-command", ".", map[string]string{})
+	err := runner.RunCommandInContainer("test-container", "test-command", driver.NewCommandOptions())
 
 	if err == nil {
 		t.Errorf("Expected error, got nil.")
@@ -37,7 +37,7 @@ func TestRunnerRunCommandInContainerReturnsErrorIfCommandExitCodeNonzero(t *test
 		Driver: &mockDriver,
 	}
 
-	err := runner.RunCommandInContainer("test-container", "test-command", ".", map[string]string{})
+	err := runner.RunCommandInContainer("test-container", "test-command", driver.NewCommandOptions())
 
 	if err == nil {
 		t.Errorf("Expected error, got nil.")

internal/workflow/models.go

@@ -17,6 +17,7 @@ type Job struct {
 	Defaults        struct {
 		Run struct {
 			WorkingDirectory string `yaml:"working-directory"`
+			Shell            string `yaml:"shell"`
 		} `yaml:"run"`
 	} `yaml:"defaults"`
 }
@@ -44,6 +45,7 @@ type Step struct {
 	WorkingDirectory string            `yaml:"working-directory"`
 	ContinueOnError  bool              `yaml:"continue-on-error"`
 	Env              map[string]string `yaml:"env"`
+	Shell            string            `yaml:"shell"`
 }
 
 func (s Step) Validate() []error {
@@ -99,6 +101,26 @@ func (w Workflow) GetEnv(jobName string, stepIndex int) map[string]string {
 	return finalEnv
 }
 
+// Returns the shell defined for the given job's step.
+// Overriding values are considered in the order: step, job, global.
+//
+// If the shell is undefined in all cases, "bash" is used.
+func (w Workflow) GetShell(jobName string, stepIndex int) string {
+	var shell string
+
+	if stepShell := w.Jobs[jobName].Steps[stepIndex].Shell; stepShell != "" {
+		shell = stepShell
+	} else if jobShell := w.Jobs[jobName].Defaults.Run.Shell; jobShell != "" {
+		shell = jobShell
+	}
+
+	if shell == "" {
+		return "bash"
+	}
+
+	return shell
+}
+
 func (w Workflow) Validate() []error {
 	validationErrors := []error{}
 

internal/workflow/models_test.go

@@ -206,3 +206,60 @@ func TestStepEnvOverwritesJobEnv(t *testing.T) {
 		t.Errorf("Unexpected env: %#v", env)
 	}
 }
+
+func TestStepShellOverridesAllOtherShellValues(t *testing.T) {
+	type TestCase struct {
+		sample string
+		name   string
+	}
+	testCases := []TestCase{
+		{sample: `
+    jobs:
+        jobA:
+            defaults:
+                run:
+                    shell: "job"
+            runs-on: default
+            steps:
+              - run: echo "test"
+                shell: "step"
+                `, name: "With job default"}, {
+			sample: `
+    jobs:
+        jobA:
+            runs-on: default
+            steps:
+              - run: echo "test"
+                shell: "step"
+                `, name: "Without job default"},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			workflow, _ := FromYamlBytes([]byte(testCase.sample))
+
+			shell := workflow.GetShell("jobA", 0)
+
+			if shell != "step" {
+				t.Errorf("Unexpected shell: %#v", shell)
+			}
+		})
+	}
+}
+
+func TestStepShellDefaultsToBash(t *testing.T) {
+	sample := `
+    jobs:
+        jobA:
+            runs-on: default
+            steps:
+              - run: echo "test"
+`
+	workflow, _ := FromYamlBytes([]byte(sample))
+
+	shell := workflow.GetShell("jobA", 0)
+
+	if shell != "bash" {
+		t.Errorf("Unexpected shell: %#v", shell)
+	}
+}